1. Field of the Invention
This invention relates to an ultrasonic diagnostic apparatus, more particularly to an improved ultrasonic diagnostic apparatus which in addition to velocity information is capable of measuring and displaying the amount of deviation of a signal in respect of the diagnostically useful information of average velocity (also average frequency) of moving objects within a living organism.
2. Description of the Prior Art
The ultrasonic pulse-Doppler method has been practically applied to the measurement of the velocity of movement of a body organ such as the heart, of blood flowing in the blood vessels or of other body fluids. The conventionaI apparatus for applying this method electrically detects the velocity of movement from the frequency shift of an echo reflected from the moving member within the living body but has been capable of detecting the velocity of movement only at a specific point at a prescribed depth within the organism. Such an ultrasonic pulse-Doppler apparatus of an advanced type for obtaining the velocity distribution of the bloodflow or the like over a wide region has been proposed by the present inventors in Japanese Patent No. 70479/1982 (Publication No. 188433/1983). This apparatus is not, however, able to obtain the velocity deviation distribution. The deviation in the Doppler frequency generally expresses spectral spread. It is a quantity which shows whether the flow of the blood is laminar or turbulent, and the condition of the turbulence. The quantity known as standard deviation value or spread shows the amount of deviation.